U.S. patent application number 14/288476 was filed with the patent office on 2015-05-14 for crosslinked speek cation exchange membrane having improved chemical stability by radiation and method of preparing the same.
This patent application is currently assigned to KOREA ATOMIC ENERGY RESEARCH INSTITUTE. The applicant listed for this patent is KOREA ATOMIC ENERGY RESEARCH INSTITUTE. Invention is credited to Sun-Young LEE, Junhwa SHIN, Joon Yong SOHN, Ju-Myung SONG, Hyun-Su WOO.
Application Number | 20150133570 14/288476 |
Document ID | / |
Family ID | 53044322 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150133570 |
Kind Code |
A1 |
SHIN; Junhwa ; et
al. |
May 14, 2015 |
CROSSLINKED SPEEK CATION EXCHANGE MEMBRANE HAVING IMPROVED CHEMICAL
STABILITY BY RADIATION AND METHOD OF PREPARING THE SAME
Abstract
Provided is a method of preparing a crosslinked sulfonated
poly(ether ether ketone) (SPEEK) cation exchange membrane
including: preparing a crosslinker mixture of a first crosslinker
containing two or more vinyl oxy groups and a second crosslinker
containing three or more vinyl groups; preparing a mother liquor
containing the crosslinker mixture, a SPEEK polymer substituted
with sodium, and a solvent; and casting the mother liquor and then
irradiating radiation thereon.
Inventors: |
SHIN; Junhwa; (Gwangju,
KR) ; SOHN; Joon Yong; (Jeongeup, KR) ; SONG;
Ju-Myung; (Jeollanam-do, KR) ; LEE; Sun-Young;
(Incheon, KR) ; WOO; Hyun-Su; (Gyeongsangnam-do,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA ATOMIC ENERGY RESEARCH INSTITUTE |
Daejeon |
|
KR |
|
|
Assignee: |
KOREA ATOMIC ENERGY RESEARCH
INSTITUTE
Daejeon
KR
|
Family ID: |
53044322 |
Appl. No.: |
14/288476 |
Filed: |
May 28, 2014 |
Current U.S.
Class: |
521/27 ; 264/488;
264/494 |
Current CPC
Class: |
C08J 3/24 20130101; H01M
2008/1095 20130101; C08J 3/28 20130101; C08J 2371/00 20130101; Y02E
60/50 20130101; H01M 8/1081 20130101; C08J 5/2256 20130101; H01M
8/1072 20130101; H01M 8/1025 20130101; Y02P 70/50 20151101 |
Class at
Publication: |
521/27 ; 264/494;
264/488 |
International
Class: |
C08J 5/22 20060101
C08J005/22; H01M 8/10 20060101 H01M008/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2013 |
KR |
10-2013-0136427 |
Claims
1. A method of preparing a crosslinked sulfonated poly(ether ether
ketone) (SPEEK) cation exchange membrane, the method comprising:
preparing a crosslinker mixture of a first crosslinker containing
two vinyl oxy groups and a second crosslinker containing three
vinyl groups; preparing a mother liquor containing the crosslinker
mixture, a SPEEK polymer substituted with sodium, and a solvent;
and casting the mother liquor and then irradiating radiation
thereon.
2. The method of claim 1, wherein the first crosslinker is a
compound represented by the following Chemical Formula 1.
##STR00007## (In Chemical Formula 1, A is any one selected from
##STR00008## R.sub.1 to R.sub.10 are each independently hydrogen or
(C.sub.1.about.C.sub.6) and m and n are integers of 1 to 5,
respectively.)
3. The method of claim 1, wherein in the crosslinker mixture, 60 to
95 wt % of the first crosslinker and 5 to 40 wt % of the second
crosslinker are mixed with each other.
4. The method of claim 1, wherein the mother liquor contains 0.1 to
20 wt % of the crosslinker mixture, 1 to 30 wt % of the SPEEK
polymer substituted with sodium, and 65 to 95 wt % of the
solvent.
5. The method of claim 1, wherein the first crosslinker contains
any one or at least two selected from 1,4-butanediol divinyl ether,
1,6-hexanediol ether, di(ethylene glycol)divinyl ether,
tri(ethylene glycol)divinyl ether, tetra(ethylene glycol)divinyl
ether, and 1,4-cyclohexanedimethanol divinyl ether.
6. The method of claim 1, wherein the second crosslinker contains
any one or a mixture of at least two selected from triallyl
isocyanurate and pentaerythritol triallyl ether.
7. The method of claim 1, wherein the solvent is any one or a
mixture of at least two selected from a group consisting of
N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide,
tetrahydrofuran, dimethylformamide, toluene, cyclohexane, benzene,
chlorobenzene, diphenylether, and 1,3,5-trimethylbenzene.
8. The method of claim 1, wherein the radioactive ray is any one
selected from a group consisting of gamma ray, UV ray, and electron
ray.
9. The method of claim 8, wherein the radioactive ray is the
electron ray.
10. The method of claim 1, wherein the radioactive ray is
irradiated at a dose rate of 0.1 to 10 kGy/min and an irradiation
dose of 50 to 600 kGy.
11. A crosslinked sulfonated poly(ether ether ketone) (SPEEK)
cation exchange membrane prepared by the method of claim 1.
12. A fuel cell membrane comprising the crosslinked SPEEK cation
exchange membrane of claim 11.
13. A water treatment membrane comprising the crosslinked SPEEK
cation exchange membrane of claim 11.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Korean Patent Application No. 10-2013-0136427, filed on Nov. 11,
2013, in the Korean Intellectual Property Office, the disclosure of
which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The following disclosure relates to a cation exchange
membrane usable as a fuel cell membrane, a water-treatment
membrane, or the like, and a method of preparing the same. More
particularly, the following disclosure relates to a sulfonated
poly(ether ether ketone) (SPEEK) cation exchange membrane
crosslinked using a mixture of a crosslinker containing two vinyl
oxy groups and a crosslinker containing three vinyl groups, and a
method of preparing the same.
BACKGROUND
[0003] After Maigrot and Sabate introduced an ion exchange membrane
in 1890 while removing inorganic ions from sugar syrup using
permanganic acid paper as a separation membrane, the ion exchange
membrane has been widely used in various industrial fields. A
process of separating and purifying a material using the ion
exchange membrane is simple and has excellent selectivity for a
specific ion, such that this process may be widely applied. An ion
exchange membrane capable of selectively separating cations and
anions in an aqueous solution has been widely used in a fuel cell,
a secondary battery, a flow battery, a water-splitting
electro-dialysis for recovering acid and base, diffusion dialysis
for recovering acid and metal chemical species from pickling waste
acid, an ultra pure water process, and the like.
[0004] Particularly, as uses of electronic products such as a small
sized notebook, a mobile phone, and the like, have rapidly
increased, recently, a demand for the development of the fuel cell
using the ion exchange membrane has increased.
[0005] In the fuel cell, chemical energy is changed into electric
energy by an electrochemical reaction Among the fuel cells, a
polymer electrolyte fuel cell using a cation exchange membrane has
excellent output characteristics, a low operation temperature, fast
startup and response characteristics as compared to other fuel
cells, such that the polymer electrolyte fuel cell may be variously
applied in a distributed power supply for a house or a public
building, a small power supply for electronic devices, or the like,
as well as a portable type power supply for a vehicle. This polymer
electrolyte fuel cell has been widely studied as an electrochemical
apparatus for a convenient and efficient power resource.
[0006] A polymer electrolyte used as a cation exchange resin or
cation exchange membrane in the fuel cell has been used for a long
period of time and steadily studied. A cation exchange membrane,
which is a cation exchange membrane, provides a layer for
separately maintaining fuel and an oxidant in addition to having
low resistance against diffusion of a proton from one electrode to
the other electrode. In order to obtain high efficiency of the fuel
cell, the cation exchange membrane should have high ionic
conductivity and chemical, thermal, mechanical, and electrochemical
stability. In addition, since the ionic conductivity is rapidly
decreased at the time of dehydration, the cation exchange membrane
should have resistance against dehydration.
[0007] Further, the cation exchange membrane should have durability
and thermal, physical, and chemical stability so that the fuel cell
may operate at a high temperature of 90 or more and in an
ultimately acidic environment. Therefore, in addition to research
into the cation exchange membrane, various researches into a cation
exchange membrane used in a direct methanol fuel cell (DMFC), a
polymer electrolyte membrane fuel cell (PEMFC, solid polymer
electrolyte fuel cell, solid polymer fuel cell, or cation exchange
membrane fuel cell) as a carrier transporting cations have been
recently conducted.
[0008] Currently, as the cation exchange membrane widely and
commonly used in a fuel cell field, there is Nafion.RTM. (Dupont,
USA), which is a perfluoro sulfonic acid based cation exchange
membrane. This fluorine based polymer has excellent mechanical
properties, chemical stability, and ion conductivity but has
disadvantages such as complicated synthetic materials or
fabrication process, a high production cost, a low driving
temperature (<100.degree. C.), low stability in methanol, and
the like.
[0009] Therefore, in order to overcome these disadvantages, a
cation exchange membrane using a cheap hydrocarbon based polymer
having excellent physical properties has been actively developed. A
representative example of the hydrocarbon based polymer may include
sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(aryl
ether sulfone), a sulfonated phenol formal resin, sulfonated
poly(phenylene oxide), phosphonic poly(phenylene oxide), sulfonated
poly(benzylimidazole), and the like.
[0010] However, since ion conductivity of the cation exchange
membrane as described above is in proportion to a sulfonation
degree, in the case in which the sulfonation degree exceeds
critical concentration, a decreased in a molecular weight may be
inevitable. In addition, the mechanical properties of the cation
exchange membrane may be decreased after being hydrated, and in
this case, the membrane may not be used for a long time. In order
to solve these problems, a method of preparing a polymer by using a
sulfonated monomer and a method of selectively sulfonating a
polymer have been developed (U.S. Pat. Nos. 5,468,574, 5,679,482,
and 6,110,616), but the problem such as stability at a high
temperature and problems generated at the time of use for a long
period of time have not been completely solved.
[0011] A cation exchange membrane using sulfonated poly(ether ether
ketone) (SPEEK) among the hydrocarbon based polymers has excellent
mechanical properties and thermal stability and may be cheaply
prepared. However, in the case of excessively introducing a
sulfonic acid group in order to improve ion conductivity, since
SPEEK excessively absorbs water, the mechanical strength and
dimensional stability of the cation exchange membrane are rapidly
decreased, such that there is a limitation in using the cation
exchange membrane as a fuel cell membrane. In order to solve this
problem, research into a technology of introducing a crosslinking
structure in SPEEK to improve dimensional stability, mechanical
property, and chemical stability under fuel cell driving conditions
has been actively conducted.
[0012] In order to introduce a crosslinking structure in a
hydrocarbon based polymer electrolyte membrane for a fuel cell,
various methods such as a method of using heat or ultraviolet (UV)
rays, and the like, have been used. In the case of crosslinking by
means of heat, a long crosslinking process at a high temperature is
required, and in the case of crosslinking by means of UV rays, it
may be impossible to form a uniform crosslinking structure due to
contamination caused by use of an initiator and low transmittance.
Meanwhile, a crosslinking technology using radiation has
advantageous in that the initiator is not required, a dense
crosslinking structure may be formed up to an internal portion of a
polymer electrolyte membrane due to high transmittance of the
radiation, and a time consumed in a preparation process may be
decreased.
[0013] The present inventor has developed a hydrocarbon based
polymer electrolyte membrane having improved thermal stability and
dimensional stability by mixing a crosslinker mixture having a
vinyl ester structure and a hydrocarbon based polymer and
irradiation (Korean Patent No. 10-1267979). However, in the
hydrocarbon based polymer electrolyte membrane, in the case of
using an ester group in a crosslinker structure for a long period
of time, the crosslinker may be decomposed. Therefore, research
into a novel material capable of having excellent thermal,
mechanical, and chemical stability and increasing dimensional
stability by introducing a crosslinking structure in a hydrocarbon
based polymer electrolyte membrane using radiation and capable of
being easily prepared has been urgently demanded.
SUMMARY
[0014] An embodiment of the present invention is directed to
providing a crosslinked sulfonated poly(ether ether ketone) (SPEEK)
cation exchange membrane having excellent chemical stability as
well as mechanical properties and dimensional stability, and a
method of preparing the same.
[0015] An embodiment of the present invention is also directed to
providing a fuel cell membrane or a water treatment membrane using
the cation exchange membrane.
[0016] In one general aspect, a method of preparing a crosslinked
SPEEK cation exchange membrane includes: preparing a crosslinker
mixture of a first crosslinker containing two vinyl oxy groups and
a second crosslinker containing three vinyl groups; preparing a
mother liquor containing the crosslinker mixture, a SPEEK polymer
substituted with sodium, and a solvent; and casting the mother
liquor and then irradiating radiation thereon.
[0017] The first crosslinker may be a compound represented by the
following Chemical Formula 1.
##STR00001##
[0018] (In Chemical Formula 1, A is any one selected from
##STR00002##
R.sub.1 to R.sub.10 are each independently hydrogen or
(C.sub.1.about.C.sub.6) and m and n are integers of 1 to 5,
respectively.)
[0019] In the crosslinker mixture, 60 to 95 wt % of the first
crosslinker and 5 to 40 wt % of the second crosslinker may be mixed
with each other.
[0020] The mother liquor may contain 0.1 to 20 wt % of the
crosslinker mixture, 1 to 30 wt % of the SPEEK polymer substituted
with sodium, and 65 to 95 wt % of a solvent.
[0021] The first crosslinker may contain any one or at least two
selected from 1,4-butanediol divinyl ether, 1,6-hexanediol ether,
di(ethylene glycol)divinyl ether, tri(ethylene glycol)divinyl
ether, tetra(ethylene glycol)divinyl ether, and
1,4-cyclohexanedimethanol divinyl ether.
[0022] The second crosslinker may contain any one or a mixture of
at least two selected from triallyl isocyanurate and
pentaerythritol triallyl ether.
[0023] The solvent may be any one or a mixture of at least two
selected from a group consisting of N,N-dimethylacetamide,
N-methyl-2-pyrrolidone, dimethylsulfoxide, tetrahydrofuran,
dimethylformamide, toluene, cyclohexane, benzene, chlorobenzene,
diphenylether, and 1,3,5-trimethylbenzene.
[0024] The radioactive ray may be any one selected from a group
consisting of gamma ray, UV ray, and electron ray.
[0025] The radioactive ray may be irradiated at a dose rate of 0.1
to 10 kGy/min and an irradiation dose of 50 to 600 kGy.
[0026] In another general aspect, there is provided a crosslinked
sulfonated poly(ether ether ketone) (SPEEK) cation exchange
membrane prepared by the method as described above.
[0027] In another general aspect, there is provided a fuel cell
membrane comprising the crosslinked SPEEK cation exchange membrane
as described above
[0028] In another general aspect, there is provided a water
treatment membrane comprising the crosslinked SPEEK cation exchange
membrane as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic view showing a process of preparing a
crosslinked SPEEK cation exchange membrane according to the present
invention.
[0030] FIG. 2 is a graph obtained by measuring a gel-fraction of a
crosslinked SPEEK cation exchange membrane according to Examples of
the present invention.
[0031] FIG. 3 is a graph obtained by measuring ion-exchange
capacity of crosslinked SPEEK cation exchange membranes according
to Examples of the present invention and Comparative Examples.
[0032] FIG. 4 is a graph obtained by measuring water uptake of the
crosslinked SPEEK cation exchange membrane according to Example of
the present invention.
[0033] FIG. 5 shows results obtained by measuring ioninc
conductivity of the cation exchange membrane according to Example
of the present invention.
[0034] FIG. 6 shows results by evaluating chemical stability of the
crosslinked SPEEK cation exchange membrane according to Example of
the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0035] Hereinafter, a method of preparing a crosslinked SPEEK
cation exchange membrane according to the present invention will be
described in detail. The exemplary embodiments of the present
invention to be described below are provided by way of example so
that the idea of the present invention can be sufficiently
transferred to those skilled in the art to which the present
invention pertains. Here, technical terms and scientific terms used
in the present specification have the general meaning understood by
those skilled in the art to which the present invention pertains
unless otherwise defined, and a description for the known function
and configuration obscuring the present invention will be omitted
in the following description.
[0036] The method of preparing a crosslinked SPEEK cation exchange
membrane according to the present invention may include:
[0037] (step 1) preparing a crosslinker mixture of a first
crosslinker containing two vinyl oxy groups and a second
crosslinker containing three vinyl groups;
[0038] (step 2) preparing a mother liquor containing the
crosslinker mixture, a SPEEK polymer substituted with sodium, and a
solvent; and
[0039] (step 3) casting the mother liquor and then irradiating
radiation thereonto.
[0040] In detail, in the present invention, step 1 is a step of
preparing the crosslinker mixture in order to improve dimensional
stability of the cation exchange membrane.
[0041] The first crosslinker may be a compound represented by the
following Chemical Formula 1.
##STR00003##
[0042] (In Chemical Formula 1, A is any one selected from
##STR00004##
R.sub.1 to R.sub.10 are each independently hydrogen or
(C.sub.1.about.C.sub.6) and m and n are integers of 1 to 5,
respectively.)
[0043] In this case, in the first crosslinker of Chemical Formula
1, A may be, for example, a compound represented by Chemical
Formulas 2 to 7, but is not necessarily limited thereto.
##STR00005##
[0044] The first crosslinker may be any one or at least two
selected from a group consisting of 1,4-butanediol divinyl ether,
1,6-hexanediol divinyl ether, di(ethylene glycol)divinyl ether,
tri(ethylene glycol)divinyl ether, tetra(ethylene glycol)divinyl
ether, and 1,4-cyclohexanedimethanol divinyl ether, but is not
necessarily limited thereto.
[0045] The second crosslinker may be any one or a mixture of at
least two selected from compounds represented by the following
Chemical Formulas 8 and 9.
##STR00006##
[0046] The second crosslinker may be any one or a mixture of at
least two selected from a group consisting of triallyl isocyanurate
(TAIC) and pentaerythritol triallyl ether (PETALE), but is not
necessarily limited thereto.
[0047] In the present invention, the crosslinker mixture may
improve mechanical strength and may be a mixture in which 60 to 95
wt % of the first crosslinker and 5 to 40 wt % of the second
crosslinker are mixed with each other in order to secure excellent
thermal, chemical, and electrochemical stability. More preferably,
the crosslinker mixture may be a mixture in which 80 to 90 wt % of
the first crosslinker and 10 to 20 wt % of the second crosslinker
are mixed with each other in order to further improve a
gel-fraction and dimensional stability of the crosslinked SPEEK
cation exchange membrane to secure excellent mechanical properties
and electrochemical stability.
[0048] In the case in which a content of the first crosslinker is
less than 60 wt %, physical strength may be increased, but
flexibility may be decreased, such that the prepared membrane may
be easily broken, and in the case in which the content is more than
95 wt %, flexibility may be increased, but it may be difficult to
secure dimensional stability.
[0049] Further, in the case in which a content of the second
crosslinker is less than 5 wt %, mechanical strength and
dimensional stability may be deteriorated, and in the case in which
the content is more than 40 wt %, crosslinking density is
excessively increased, such that impact strength may be
deteriorated.
[0050] In the present invention, step 2 is a step of preparing the
mother liquor of a SPEEK cation exchange membrane substituted with
sodium. More specifically, the mother liquor may be prepared by
dissolving the SPEEK polymer substituted with sodium and the
crosslinker mixture prepared in step 1 in the solvent at room
temperature.
[0051] As an aspect of the SPEEK polymer substituted with sodium of
step 2, protons of a sulfonic acid group may be substituted with a
sodium ion by dipping the SPEEK polymer in 1M sodium chloride for
12 to 48 hours. In the case in which the proton of the sulfonic
acid group is not substituted with sodium, a vinyl ether
crosslinker may be hydrolyzed due to the proton of the sulfonic
acid group during a process of evaporating the solvent. In
addition, the SPEEK polymer may be substituted with a proton or
alkali metal ion form as well as the sodium ion. In this case,
reactivity with the crosslinker mixture may be improved.
[0052] As the solvent, any one or a mixture of at least two
selected from a group consisting of N,N-dimethylacetamide (DMAc),
N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO),
tetrahydrofuran, dimethylformamide, toluene, cyclohexane, benzene,
chlorobenzene, diphenylether, and 1,3,5-trimethylbenzene may be
used. Preferably, a polar solvent such as N,N-dimethylacetamide
(DMAc), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), and
the like, may be used alone, or a mixture thereof may be used, but
the present invention is not necessarily limited thereto.
[0053] In the present invention, the mother liquor may contain 0.1
to 20 wt % of the crosslinker mixture, 1 to 30 wt % of the SPEEK
polymer substituted with sodium, and 65 to 95 wt % of the solvent.
In this case, when a content of the solvent is less than 65 wt %,
dispersibility may be deteriorated, and crosslinking density may be
increased, and when the content is more than 95 wt %, it may be
difficult to form a membrane.
[0054] In step 2 of the present invention, the SPEEK polymer
substituted with sodium may form a backbone of the cation exchange
membrane. In addition to the SPEEK polymer substituted with sodium,
another polymer such as a sulfonated poly(aryl ether sulfone)
polymer substituted with sodium, a sulfonated poly(imide) polymer
substituted with sodium, a sulfonated poly(phenylene oxide)
substituted with sodium, or the like, may be used, but the present
invention is not necessarily limited thereto.
[0055] In this case, the SPEEK polymer substituted with sodium may
be contained at a content of 5 to 30 wt % based on a total weight
of the mother liquor. In the case in which the content of the SPEEK
polymer substituted with sodium is less than 5 wt %, the cation
exchange membrane may not have sufficient ion conductivity, and in
the case in which the content is more than 30 wt %, dimensional
stability may be deteriorated.
[0056] In the present invention, step 3 is a step of casting the
mother liquor and then irradiating the cast mother liquor. More
specifically, step 3 may include, after a step of casting and
drying the mother liquor onto a glass plate, a step of irradiating
and drying the mother liquor.
[0057] As an aspect of the process of casting and drying the mother
liquor, the mother liquor is uniformly sprayed onto a glass plate
having a suitable size at room temperature using a solution casting
method and then dried at 60 to 80.degree. C. for 1 to 2 hours,
thereby evaporating the solvent. In the case of performing the
drying process under the above-mentioned conditions, the solvent
partially remains, such that the formed membrane has a viscosity at
which the solution does not flow.
[0058] The membrane prepared by casting and then drying the mother
liquor is irradiated, such that the crosslinker and the SPEEK
polymer substituted with sodium are crosslinked to each other,
thereby making it possible to improve mechanical strength. As an
aspect, the crosslinked SPEEK cation exchange membrane may be
prepared by irradiating the membrane formed on the glass plate by
evaporating the solvent, vacuum-drying the irradiated membrane at
100 to 140.degree. C. for 10 to 14 hours to remove the remaining
solvent, followed by cooling to room temperature and separating the
prepared crosslinked SPEEK cation exchange membrane from the glass
plate using distilled water.
[0059] As the radiation, any one or more selected from a group
consisting of gamma rays, UV rays, and electron rays may be
irradiated. Preferably, the electron ray may be irradiated.
[0060] In addition, the radiation may be irradiated at a dose rate
of 0.1 to 10 kGy/min and an irradiation dose of 50 to 600 kGy.
Preferably, the radiation may be irradiated at a dose rate of 1 to
7 kGy/min and an irradiation dose of 200 to 400 kGy.
[0061] In the case in which the irradiation dose of the radiation
is less than 50 kGy, sufficient crosslinking is not performed, and
in the case in which the irradiation dose is more than 600 kGy,
breakage between molecules may be generated, such that mechanical
strength may be deteriorated due to a decrease in a molecular
weight.
[0062] The method of preparing a crosslinked SPEEK cation exchange
membrane according to the present invention may further include,
after step 3, a process of removing impurities by washing and
drying the crosslinked SPEEK cation exchange membrane. As an aspect
of the process of removing the impurities, the prepared cation
exchange membrane may be dipped in 0.5 to 2M aqueous HCl solution
for 12 to 72 hours to remove the impurities, sodium may be
substituted with hydrogen, and then the obtained cation exchange
membrane may be dried.
[0063] The crosslinked SPEEK cation exchange membrane prepared
according to the present invention by mixing the crosslinker
mixture composed of the first crosslinker containing two or more
vinyl oxy groups and the second crosslinker containing three or
more vinyl groups with the SPEEK polymer substituted with sodium at
a suitable composition ratio and irradiating radiation may be
prepared at room temperature in a short time and maintain high
ionic conductivity in addition to a sufficient gel fraction and
high chemical stability and dimensional stability, such that the
crosslinked SPEEK cation exchange membrane may be applied as an ion
exchange membrane, the fuel cell membrane, the flow battery
membrane for a high capacitance secondary battery, the water
treatment membrane, and the like, in various industrial fields.
[0064] Hereinafter, the present invention will be described in
detail through Examples. However, the following Examples are to
illustrate the present invention, and the scope of the present
invention is not limited to the following Examples.
Example 1
Preparation of Polymer Electrolyte Membrane Using Crosslinked SPEEK
as Basic Backbone by Irradiation Crosslinking Method
[0065] A crosslinked SPEEK cation exchange membrane according to
the present invention, having improved thermal stability and
dimensional stability by using sulfonated poly(ether ether ketone)
(SPEEK) as a basic backbone was prepared as shown in FIG. 1.
[0066] Step 1. Preparing of Crosslinker Mixture
[0067] 1,4-butanediol divinyl ether and trially isocyanurate were
mixed at a weight mixing ratio of 9:1, thereby preparing a
crosslinker mixture at room temperature.
[0068] Step 2. Preparing of Mother Liquor
[0069] Sulfonated SPEEK substituted with sodium and the crosslinker
mixture prepared in step 1 were mixed in N,N-dimethylacetamide
(DMAc) at a composition ratio shown in the following Table 1,
thereby preparing a mother liquor at room temperature.
[0070] Step 3. Casting and Drying of Mother Liquor onto Glass
Plate
[0071] The mother liquor prepared in step 2 was uniformly sprayed
onto a glass plate (15 cm.times.15 cm) at room temperature using a
solution casting method. The glass plate onto which the mother
liquor was sprayed was dried at a high temperature of 70.degree.
C., thereby evaporating N,N-dimethylacetamide (DMAc) for 1
hour.
[0072] Step 4. Irradiating and Drying Glass Plate
[0073] Electron ray was irradiated onto the glass plate on which
the solvent was evaporated at a dose rate of 6 kGy/min and an
irradiation dose shown in Table 1. The irradiated glass plate was
vacuum-dried at 100.degree. C. for about hours to remove the
remaining DMAc solvent and then cooled to room temperature. Then,
the prepared polymer electrolyte membrane was separated from the
glass plate using distilled water. Finally, the prepared polymer
electrolyte membrane was put into 1M aqueous HCl solution for 48
hours to remove impurities, thereby preparing a crosslinked SPEEK
cation exchange membrane according to the present invention.
Examples 2 to 20
[0074] The same method as that in Example 1 was performed using
compositions shown in the following Table 1.
TABLE-US-00001 TABLE 1 Content of Content of Irradiation Content of
crosslinker solvent dose Classification SPEEK (wt %) mixture (wt %)
(wt %) (kGy) Example 1 10 0.5 89.5 50 Example 2 10 0.5 89.5 100
Example 3 10 0.5 89.5 200 Example 4 10 0.5 89.5 300 Example 5 10
1.1 88.9 50 Example 6 10 1.1 88.9 100 Example 7 10 1.1 88.9 200
Example 8 10 1.1 88.9 300 Example 9 10 2.5 87.5 50 Example 10 10
2.5 87.5 100 Example 11 10 2.5 87.5 200 Example 12 10 2.5 87.5 300
Example 13 10 4.3 85.7 50 Example 14 10 4.3 85.7 100 Example 15 10
4.3 85.7 200 Example 16 10 4.3 85.7 300 Example 17 10 6.7 83.3 50
Example 18 10 6.7 83.3 100 Example 19 10 6.7 83.3 200 Example 20 10
6.7 83.3 300
Examples 21 to 26
[0075] The same method as that in Example 16 was performed using
the compositions shown in the following Table 2 while changing a
mixing ratio of the first crosslinker and the second crosslinker in
the crosslinker mixture.
TABLE-US-00002 TABLE 2 Content of crosslinker mixture (wt %)
Content 1,4- Content of Butanediol of Irradiation SPEEK divinyl
Trially solvent dose Classification (wt %) ether isocyanurate (wt
%) (kGy) Example 10 4.085 0.215 85.7 300 21 Example 10 3.440 0.860
85.7 300 22 Example 10 3.010 1.290 85.7 300 23 Example 10 2.580
1.720 85.7 300 24 Example 10 4.150 0.150 85.7 300 25 Example 10
2.150 2.150 85.7 300 26
Comparative Example 1
Preparation of Sulfonated poly(ether ether ketone) Cation Exchange
Membrane
[0076] A polymer electrolyte membrane having a hydrocarbon based
crosslinking structure using sulfonated poly(ether ether ketone)
(SPEEK) substituted with sodium as a basic backbone was
prepared.
[0077] Step 1. Preparing of Mother Liquor
[0078] 90 wt % of N,N-dimethylacetamide (DMAc) and 10 wt % of SPEEK
were mixed with each other, thereby preparing a mother liquor at
room temperature.
[0079] Step 2. Casting and Drying of Mother Liquor onto Glass
Plate
[0080] The mother liquor prepared in step 1 was uniformly sprayed
onto a glass plate (15 cm.times.15 cm) at room temperature using a
solution casting method. The glass plate onto which the mother
liquor was sprayed was vacuum-dried at 120.degree. C. for about 12
hours to remove the remaining DMAc and then cooled to room
temperature. Then, the prepared polymer electrolyte membrane was
separated from the glass plate using distilled water. Finally, the
prepared polymer electrolyte membrane was put into 1M aqueous HCl
solution for 48 hours to remove impurities, thereby preparing a
crosslinked SPEEK cation exchange membrane of Comparative
Example.
Comparative Example 2
Preparation of Sulfonated poly(ether ether ketone) Cation Exchange
Membrane
[0081] The same method as that in Example 16 was performed except
for using a mother liquor obtained by mixing 85.7 wt % of
N,N-dimethylacetamide (DMAc) and 10 wt % of SPEEK with 4.3 wt % of
divinylbenzene (DVB) as a crosslinker at room temperature.
Comparative Example 3
Preparation of Sulfonated poly(ether ether ketone) Cation Exchange
Membrane
[0082] The same method as that in Example 16 was performed except
for using a mother liquor obtained by mixing 85.7 wt % of
N,N-dimethylacetamide (DMAc) and 10 wt % of SPEEK with 4.3 wt % of
1,4-butanediol divinyl ether as a crosslinker at room
temperature.
Comparative Example 4
Preparation of Sulfonated poly(ether ether ketone) Cation Exchange
Membrane
[0083] The same method as that in Example 16 was performed except
for using a mother liquor obtained by mixing 85.7 wt % of
N,N-dimethylacetamide (DMAc) and 10 wt % of SPEEK with 4.3 wt % of
trially isocyanurate as a crosslinker at room temperature.
Experimental Example 1
Measurement Gel-Fraction
[0084] In order to confirm gel-fractions of the crosslinked SPEEK
cation exchange membranes prepared in Examples and Comparative
Examples, experiments were performed as follows. In detail, after
dipping the crosslinked SPEEK cation exchange membranes prepared in
Examples and Comparative Examples into DMAc, which is a solvent
used before irradiating the electron rays, for one day, changes in
the weight were observed, and then gel-fractions were calculated by
the following Equation 1. The results were shown in FIG. 2.
Gel Fraction ( % ) = W dry - W dissolved W dry .times. 100 [
Equation 1 ] ##EQU00001##
[0085] In Equation 1, W.sub.dry is a weight of the crosslinked
SPEEK cation exchange membrane before dipping it in DMAc, and
W.sub.dissolved is a weight of the crosslinked SPEEK cation
exchange membrane after dipping it in DMAc for 1 day.
[0086] FIG. 2 is a graph obtained by measuring the gel-fraction of
the crosslinked cation exchange membrane according to Example of
the present invention. It may be confirmed that in the case in
which an irradiation dose was 200 kGy or more, the gel fraction of
the crosslinked cation exchange membrane was over 40%, such that
the crosslinked cation exchange membrane had a sufficient gel
fraction.
[0087] Table 3 shows results obtained by measuring the
gel-fractions of the prepared crosslinked SPEEK cation exchange
membrane. As shown in the following Table 3, in the crosslinked
SPEEK cation exchange membrane of Comparative Example 2 prepared
using divinyl benzene, which is mainly used as an irradiation
crosslinker, as a crosslinker, the gel fraction was less than 10%,
which was lower than the gel fraction in Example. Further, in the
crosslinked SPEEK cation exchange membrane of Comparative Example 2
prepared using only the first crosslinker and the crosslinked SPEEK
cation exchange membrane of Comparative Example 4 prepared using
only the second crosslinker, low gel-fractions (about 20%) were
obtained. On the contrary, it may be confirmed that in the
crosslinked SPEEK cation exchange membranes of Examples prepared
using the mixture of the first and second crosslinkers, a
crosslinking structure may be more easily formed by irradiation as
compared to the crosslinked SPEEK cation exchange membranes of
Comparative Examples 3 and 4 respectively prepared using the first
crosslinker alone and the second crosslinkers alone.
TABLE-US-00003 TABLE 3 Crosslinker 1,4- Trially Irradi- Gel-
Butanediol isocyan- Divinyl ation frac- Classifi- divinyl urate
benzene dose tion cation SPEEK ether (wt %) (wt %) (wt %) (kGy) (%)
Comparative 10 0 0 0 0 0 Example 1 Comparative 10 0 0 4.3 300 7.82
Example 2 Comparative 10 4.3 0 0 300 22.34 Example 3 Comparative 10
0 4.3 0 300 20.48 Example 4 Example 16 10 3.870 0.430 0 300 69.20
Example 21 10 4.085 0.215 0 300 65.53 Example 22 10 3.440 0.860 0
300 49.10 Example 23 10 3.010 1.290 0 300 39.10 Example 24 10 2.580
1.720 0 300 34.56 Example 25 10 3.150 0.150 0 300 24.52 Example 26
10 2.150 2.150 0 300 25.62
Experimental Example 2
Measurement of Ion Exchange Capacity (IEC)
[0088] In order to confirm IEC of the crosslinked cation exchange
membranes prepared in Examples 4, 8, 12, 16, and 20, experiments
were performed using a neutralization titration method as follows.
In detail, the crosslinked cation exchange membranes prepared in
Examples 4, 8, 12, 16, and 20 were put into 3M NaCl solution for 24
hours to neutralize H+ of the sulfonic group into Na+ form, and
then reverse neutralization titration was performed using 0.1M
NaOH. An automatic titrator DL22 (Mettler Toledo Company,
Switzerland) was used for accurate neutralization titration. IEC
values were calculated using the following Equation 2, and the
results were shown in FIG. 3.
IEC ( meq / g ) = C NaOH - V NaOH W dry [ Equation 2 ]
##EQU00002##
[0089] In Equation 2, C.sub.NaOH is a concentration of NaOH
solution, V.sub.NaOH is a volume of 0.1M NaOH solution used in the
neutralization titration, and W.sub.dry is a weight of the
crosslinked cation exchange membrane in a dry state.
[0090] FIG. 3 is a graph obtained by measuring ion exchange
capacity of the cation exchange membranes having the crosslinking
structure prepared according to Examples of the present invention
and Comparative Examples. It may be confirmed that the ion exchange
capacity of the cation exchange membranes prepared by the radiation
crosslinking method in Examples 4, 8, 12, 16, and 20 was 1.3 meq/g
or more.
Experimental Example 3
Measurement of Water Uptake
[0091] In order to confirm water uptake of the cation exchange
membranes prepared in Comparative Example 1 and Examples 4, 8, 16,
and 20, experiments were performed as follows. In detail, after the
cation exchange membranes prepared in Comparative Example 1 and
Examples 4, 8, 16, and 20 were put into distilled water at 30, 50,
and 70.degree. C., water remaining in surfaces of the cation
exchange membranes was removed, and changes in the weight were
observed. Then, water uptake was calculated using the following
Equation 3, and the results were shown in FIG. 4.
Water Uptake ( % ) = W s - W d W d .times. 100 [ Equation 3 ]
##EQU00003##
[0092] Here, W.sub.d is a weight of the dried membrane, and W.sub.s
is a weight of the membrane absorbing water.
[0093] FIG. 4 is a graph obtained by measuring water uptake of the
cation exchange membrane according to Examples of the present
invention. It may be confirmed that the water uptake was increased
as the temperature of the cation exchange membrane prepared in
Comparative Example 1 and Examples 4, 8, 12, 16, and 20 was
increased. Meanwhile, it may be confirmed that the water uptake was
decreased in accordance with the increase of the content of the
crosslinker.
Experimental Example 4
Measurement of Ionic Conductivity
[0094] In order to confirm ionic conductivity of the polymer
electrolyte membranes prepared in Example, experiments were
performed as follows. In detail, resistance of the cation exchange
membranes prepared in Examples 4, 8, 12, 16, and 20 was measured
using an AC impedance analyzer (SI 1260, Solatron Company). In this
case, impedance was measured according to the change in a
temperature in a frequency range of 0.01 to 100 kHz, and the ionic
conductivity was calculated using the following Equation 4. The
results were shown in FIG. 5.
Proton Conductivity ( .sigma. , S / cm ) = L A .times. R [ Equation
4 ] ##EQU00004##
[0095] In Equation 4, L is a distance between two electrodes, A is
an area of the polymer electrolyte membrane in a thickness
direction, and R is electric resistance.
[0096] FIG. 5 is a graph obtained by measuring ionic conductivity
of the cation exchange membrane according to Examples of the
present invention. It may be confirmed that the crosslinked ionic
conductivity of the cation exchange membrane prepared in Examples
4, 8, 12, 16, and 20 was increased in accordance with the increase
of the temperature. In addition, it may be confirmed that the ionic
conductivity of all of the crosslinked cation exchange membranes
was 10.sup.-2 S/cm or more.
Experimental Example 5
Evaluation of Chemical Stability (Fenton's Reagent Test)
[0097] In order to confirm chemical stability of the cation
exchange membranes prepared in Comparative Example 1 and Examples
4, 8, 12, 16, and 20, experiments were performed as follows. In
detail, the crosslinked cation exchange membranes prepared in
Examples 4, 8, 12, 16, and 20 and the cation exchange membrane
prepared in Comparative Example 1 were put into distilled water for
one day, such that the cation exchange membranes were sufficiently
swelled. An initial weight of the swelled electrolyte membrane was
measured (in this case, measurement was performed after water in
the surface of the electrolyte membrane was sufficiently removed as
the same method as in the method of measuring the water uptake in
Experimental Example 3). Then, the swelled electrolyte membrane was
put into a solution obtained by adding Fe.sup.2+ (8 ppm), that is,
Fenton's reagent to H.sub.2O.sub.2 (6%) at 60.degree. C.
Thereafter, a change in the weight of the polymer electrolyte
membrane as measured every 30 minutes, and the results were shown
in FIG. 6. Chemical stability was evaluated by confirming these
results.
[0098] As shown in FIG. 6, the weight of the SPEEK electrolyte
membrane to which the crosslinker was not added was rapidly
decreased after 30 minutes, such that after 60 minutes, chemical
stability was decreased at a degree at which it was impossible to
measure the change in the weight. On the other hand, it may be
appreciated that in the case of the polymer electrolyte membrane in
Example 20 according to the present invention, the change in the
weight may be measured up to 180 minutes, such that the chemical
stability was increased in accordance with the increase of the
crosslinker.
[0099] Therefore, the crosslinked SPEEK cation exchange membrane
prepared according to the present invention by mixing the
crosslinker mixture composed of the first crosslinker containing
two vinyl oxy groups and the second crosslinker containing three
vinyl groups with the SPEEK polymer substituted with sodium at a
suitable composition ratio and irradiating radiation may be
prepared at room temperature in a short time and maintain high
ionic conductivity in addition to a sufficient gel fraction and
high chemical stability and dimensional stability, such that the
crosslinked SPEEK cation exchange membrane may be applied as the
ion exchange membrane, the fuel cell membrane, the flow battery
membrane for a high capacitance secondary battery, the water
treatment membrane, and the like, in various industrial fields.
[0100] In the method of preparing a crosslinked SPEEK cation
exchange membrane according to the present invention, the ion
exchange membrane may be prepared at room temperature in a short
time.
[0101] In addition, the crosslinked SPEEK cation exchange membrane
according to the present invention may have excellent chemical,
thermal, mechanical, and electrochemical stability while
significantly increasing a gelation and dimensional stability.
[0102] Further, the crosslinked SPEEK cation exchange membrane
according to the present invention may be applied as an ion
exchange membrane, the fuel cell membrane, the flow battery
membrane for a high capacitance secondary battery, the water
treatment membrane, and the like, in various industrial fields.
[0103] Hereinabove, although the present invention is described by
restricted exemplary embodiments, they are provided only for
assisting in the entire understanding of the present invention.
Therefore, the present invention is not limited to the exemplary
embodiments. Various modifications and changes may be made by those
skilled in the art to which the present invention pertains from
this description.
[0104] Therefore, the spirit of the present invention should not be
limited to the above-mentioned exemplary embodiments, and the
following claims as well as all modified equally or equivalently to
the claims are intended to fall within the scope and spirit of the
invention.
* * * * *